A known lane-dividing line detection device detects a lane-dividing line such as a white line drawn on a road to divide lanes where vehicles run (see, for example, Patent Document 1). The device includes a camera that is installed in its own vehicle and picks up an area ahead of the vehicle and processes an image picked up by the camera to detect the lane-dividing line. Specifically, the device extracts plural parts where brightness is equal to or larger than a reference threshold as characteristic points of the lane-dividing line from the image including the lane-dividing line such as a white line and connects the plural characteristic points together with a line to set candidate lines having a large number of the characteristic points for the lane-dividing line.
Patent Document 1: JP-B2-2861638